Acetylated metallo-organic compounds and their preparation



United States Patent O ACETYLATED METALLO-ORGANIC COMPOUND AND THEIR PREPARATION William M. Sweeney, Hopewell Junction, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application February 29, 1956 Serial No. 568,435

4 Claims. (Cl. 260-429) The instant invention relates to polyacetyl dicyclopentadienyl-transition element compounds having at least three acetyl groups and process for making same.

Representative of the dicyclopentadienyl reactants use-- ful in the practice of my process is dicyclopentadienyl iron, more commonly called ferrocene. Heretofore it has been proposed to acetylate ferrocene with acetic anhydride in the presence of hydrofluoric acid. The reaction in this case yields the monoacetyl substance. The use of aluminum chloride catalyst in this reaction yields the diacetyl derivative.

Other dicyclopentadienyl-transition element compounds suitable for the practice of my process include: alkylated 2,852,542 Patented Sept. 16, 1958 ice 9 H ing it by my process, but is preferably unacetylated since -use of my process makes such step unnecessary.

In my preparation I use acetic anhydride in excess of the stoichiometric amount necessary for formation of the specific polyacetyl compound from the dicyclopentadienyl-iron compound, generally between 3 and 30 times I the stoichiometric amount, to obtain substantial utilization of the metallo-organic reactant in a reasonable reaction period. For example, in reacting dicyclopentadienyl iron to form the tetraacetyl dicyclopentadienyl iron I use at least 12 mols and advantageously about 20 mols of acetic anhydride per mol of dicyclopentadienyl iron ferrocene; substituted dicyclopentadienyl-iron compounds made from a fulvene Grignard reagent and whom salt as is shown in my copending patent application S. N.

512,873, filed June 2, 1955, entitled Organometallic Compounds and Process for Producing Same"; and dicyclopentadienyl-iron compounds characterized by a substituted two-carbon atom bridge between a pair of cyclopentadienyl rings as are shown in my copending applicacharged to the reactor; for efliciency and economy in the practice of the invention I restrict the amount of acetic anhydride in such preparation to not more than about 120 mols and preferably to not more than about '80 mols per mol of dicyclopentadienyl iron. In a similar is broadly from about 0.005 or even less, and need not be above 10.2. Preferably such mol fracton is from 0.02 to 0.05.

In order to achieve effective polyacetylation in a reasonable time the temperature of the reaction mixture should not be substantially below about 200 F. Temtion S. N. 522,867 of July 18, 1955, also entitled Organometallic Compounds and Process for Producing Same.

Broadly, my process for said polyacetylation comprises: forming a reaction mixture of the dicyclopentadienyl-iron compound, said compound having not more than two acetyl groups, and acetic anhydride in excess of the stoichiometric amount necessary for formation of the corresponding polyacetyl compound having at least three acetyl groups; heating said reaction mixture at a temperature between 200 and 350 F. in the presence of trifluoroacetic acid until said corresponding polyacetyl compound is formed; and separating said corresponding polyacetyl compound from the reaction mixture.

A particular aspect of my invention is the new compound, tetraacetyl dicyclopentadienyl iron, obtainable by my process. I have found that the trifluoroacetic acid catalyst is specific for such polyacetyl compound formation, this compound being not readily obtained using the conventional HF catalyst or acetyl chloride.

The particular polyacetylated compounds from my process exhibit solubility in both water and hydrocarbon solvents. Because of this and their chemical properties, they provide a means of aqueous-phase corrosion inhibition for, and also a means of bearing soluble metal into mixed aqueous and hydrocarbon systems such as occur in fuel tanks.

Preparation of a variety of suitable reactants for the practice of my process from a fulvene is described in the above-mentioned patent applications. conventionally dicyclopentadienyl iron can be prepared by the reaction between cyclopentadienyl Grignard reagent and an iron halide, or by the reaction of dicyclopentadienyl sodium or potassium and an iron halide, e. g. ferric chloride, in a. medium such as tetrahydrofuran. The cyclopentadienyl reactant can, if desired, be monoacetylated or diacetylated by any prior art method before polyacetylatperatures of 350 F. and higher can be used because of the thermal stability of the reactants and product. Advantageously, however, the reaction can be conducted at least in its initial stages under total reflux at the atmospheric boiling point of the reaction mixture which ordinarily will be about in the range of 280 to 300 F.

Elevated pressure is not necessary but can be desirable to maintain liquid phase conditions in the reactor at a temperature above the atmospheric boiling point of the reaction mixture. Operation at atmospheric pressure is preferred, but higher and lower pressures can be used if desired. Mechanical agitation can also be used. Generally, at least one-half hour of reaction time is needed under preferred conditions to assure economic utilization of reactants, and 1 to 6 hours is preferable in this regard.

,While the cyclopentadienyl nucleus of ferrocene has five possible positions for acetylation and the iron compounds shown in S. N. 512,873 and S. N. 522,867 have four, it is unlikely that exhaustive acetylation of all these positions is practical using my process. Tetraacetylation, however, can be obtained readily, and, with temperatures toward the lower end of the above range, e. g. ZOO-350 F., and/or short reaction times such as /2-2 hours, a substantial proportion of tri acetylated product can be formed in the reaction mixture. While it is conceivable that other lower fatty acid anhydrides such as propionic anhydride could be substituted for acetic anhydride in my process, the prospects of obtaining as much as trior tetrasubstitution in any large proportion as compared to monoor disubstitution are not as good as with acetic anhydride.

Separation of the product is done conveniently by diluting the reaction mixture with water, then extracting the product from the resulting mixture with a hydrocarbon, e. g. benzene or toluene. For economy in the operation one can strip off the bulk of the unreacted acetic anhydride and the trifluoroacetic acid catalyst from the reaction mixture by distillation, e. g. at atmospheric pressure or under reduced pressure with or without inert gas blowing, before diluting the reaction mixture with water.

When atmospheric pressure distillation is used,- the-previ-- ous reaction period can be shortened somewhat as such distillation involves additional heating of the mixture.

The hydrocarbon solution can be neutraliied, dried and the solvent evaporated to leave the'product' as residues Because of the corrosive natureof'the substanceshandled, materials of construction used in the-process-are preferably glass, glass-lined steel, porcelain'and' the'liker.

The'following equations are given to assist in under.-

standing the invention-but are not'to be construed-as lim-'- iting it. In Equation 1 ferroceneis used; in Equation 2 2,3-dimethyl, 2,3-bis (1' cyclopentadienyl) iron-butane is used; in Equation 3 the reaction product of iron chloride" and the adduct' ofethyl Grignard reagent with dimethyl' fulvene is used.

CF'sOOOH C10 H10 F6;+- 4(CHsCOhO Ferrocene Acetic anhydride Trifluoracetic acid and solvent- [(CHaCO)4.C1cHs] Fe 4 GHaCOOH' Tetraacetyl ,ferrocene Acetic acid [C10 H5 C(CHa)2C (CH3)2]FG CFSCOOH.

2,3-dimethyL2, 4(OH3OO)20 (1' cyclopentadienyl) iron-butane (A) (Solvent) {(CH3CO)i-C1UH4 C(GH3)20(OH3)2] Fe -+-4 GHaCOOH Tetraacetyl reaction product of (A) CFsCOOH Reaction product of ironchloride 3(GH3CO)2O andthe adduct .of ethyl Grignard (Solvent) reagent with dimethyl fulvene (B) [(OHsO)s.Cw H [C(CHihCzH-dg] Fe 3 CHsGOQH.

Trlacetyl derivative of (B) Even under; prolonged drastic reaction conditions; acetylation of alkyl groups on the products of Equations 2 and 3, above, is unlikely. The acetylation is believed to occur preferentially on the cyclopentadienyl nuclei. If, however, one or more of such alkyl substituents on the, cyclopentadienyl nuclei are replaced by an aromatic radical such as phenyl, acetylation can occur on both the cyclopentadienyl nucleiand such aromatic radical. Accordingly, ample acetic anhydride should be used in the reaction mixture in suchcases.

Where the metallo-organic reactant has dienyl nuclei as are describedin S. N. 512,873, and S. vN. 522,867, acet ylation can be expected to occur on such nuclei in the. same manner as it occurs on the cyclopentadienyl' nuclei of ferrocene. Tertiary alkyl amino .substituent groups-on side chains from cyclopentadienylnuclei, e. g. as in 2,3- diethylamino methyl-2,3 bis (1" cyclopentadienyl)- iron butane, resist acetylation as do alkyl substituents, but corresponding primary and secondary amino substituents will acetylate readily.

The polyacetylated product of my invention can be catalytically reduced with hydrogen or by other methods for example, with hydrazine, to provide a corresponding polyalkyl material useful in hydrocarbon fuels as an antiknock and/ or smoke suppression additive.

The points of attachment of the multiple acetyliradi- 4. calstothe-two cyclopentadienyl nucleiof. the polyacetyle ated product are not known with exactness, but it is believed that symmetrical acetyl substitution is likely to occur far more readily than unsymmetrical substitution when the product has anevertnumber of acetyl groups.

The preparation of tetraacetylferrocene by my method is=shown1below-.. Herein all parts arepartstby weight and.

all percentagesareweight percentages.

Areaction-mixture.Wasformed from 9.3 parts of ferrocene and 433 parts of aceticanhydride into which was blended 11.4 parts of trifluoroacetic acid. The-mixture was then boiled under reflux at atmospheric pressure for five hours: Thereactionmix-ture turned deeply-purple in color. It was diluted with water, then extracted with benzene. The benzene solutiomwas, washed with aqueous 5% sodium carbonate, then with water, dried and the solvent evaporated leaving purple crystals of crude tetraacetyl ferrocene having. amelting point of 72 C.

One part. of the-- crystalline tetraacetyl ferrocene was added to an aqueous-solution of 2.5 parts of hydroxylamine hydrochloride and 1.09'parts-of sodium hydroxide plus sufiicient ethanol to facilitate rapid solution of the crystals. This mixture'was warmed on asteam bath for ten minutes; then cooled'in an ice bath: to precipitate crystals of the correspondingoxime having melting point of 149 C. and analyzing to the composition of Fe(Ci H' O N4) with 52.4%-carbon and 5.3% hydrogen as compared to a calculated composition of 52.2% carbon and" 5-.3%- hydrogen.=

Obviously, many modifications and variations of the invention; as hereinb'efore set forth, may be made without. departing-'from'the spirit and scope thereof, and therefore 1 only suchlimitationsshould.be imposedtasare indicated iii-the appended claims.

I-cl'aimn 1. A process formaking a polya'cetyl dicyclopentadienyl iron compound having 3 to 4 acetyl. groups at tachedlto nucleancarbon atoms which comprises: forming-a reaction mixture of a dicyclopentadienyl iron compound, said compound'having not more-than two acetyl groups attached to nuclear carbon atoms, and acetic. anhydride in excessof the stoichiometric' amount necessary for formationof said-polyacetyllcompound;heating said. reaction mixture at aternperature between 200 and 3509' F: in the -presence oftrifiuoroacetic acid-.until'said polyacetyl' compound" is, formed; and" separating saidi poly-- acetyl compound from the reaction mixture.

2. The process-of claiml wherein the quantity of' acetic anhydride. is 3-30. times the stoichiometric' amount,- the mol' fractioniof trifluoroaceticacid' in the reaction mixture is from about 0.005 to about'0.2, andthe reaction mixture is heated for at least one-halfhour.

3. The processof claim. 2 wherein the dicyclopentadienyl reactantis dicyclopentadienyl iron.

4. Tetraacetyldicyclopentadienyl iron.

References Citedin the file of this patent Woodward et al.: Jour. Am. Chem. Soc.,'vol. 74, July5, 1952, pages 3458-9.

Patent No, 2,852,542 September 16, 1958 William M. Sweeney of the above numbered patent Patent should read as corrected below.

Column 2, line 28, for "fraoton" read fraction column 3, line 44, for clienyl" read indenyl Signed and sealed this 25th day of November 1958u (SEAL) Attest:

KARL mum ROBERT c. WATSON Attesting Ofiicer Commissioner of Patents 

1. A PROCESS FOR MAKING A POLYACETYL DICYCLOPENTADIENYL IRON COMPOUND HAVING 3 TO 4 ACETYL GROUPS ATTACHED TO NUCLEAR CARBON ATOMS WHICH COMPRISES: FORMING A REACTION MIXTURE OF A HICYCLOPENTADIENYL IRON COMPOUND, SAID COMPOUND HAVING NOT MORE THAN TWO ACETYL GROUPS ATTACHED TO NUCLEAR CARBON ATOMS, AND ACETIC ANHYDRIDE IN EXCESS OF THE STOICHIOMETRIC AMOUNT NECESSARY FOR FORMATION OF SAID POLYACETYL COMPOUND; HEATING SAID REACTION MIXTURE AT A TEMPERATURE BETWEEN 200* AND 350* F. IN THE PRESENCE OF TRIFLUOROACETIC ACID UNTIL SAID POLYACETYL COMPOUND IS FORMED; AND SEPARATING SAID POLYACETYL COMPOUND FROM THE REACTION MIXTURE. 